The Tishchenko reaction is illustrative of an early prior art method of ester synthesis. The process involves disproportionation of an aldehyde such as acetalaldehyde into the corresponding ester, e.g., ethyl acetate, in the presence of an aluminum alkoxide catalyst.
U.S. Pat. No. 1,869,761 discloses a process for vapor phase conversion of alcohols to esters in the presence of a silver-uranium carbonate catalyst.
U.S. Pat. No. 1,975,853 describes a process for producing ethyl acetate by contacting ethanol in vapor phase under high pressure with a catalyst consisting of metallic copper and a difficultly reducible oxide.
U.S. Pat. No. 2,012,993 proposes the inclusion of water in a reaction mixture of an alcohol and a dehydrogenation catalyst to suppress the formation of higher alcohols and increase the production of ester derivatives.
U.S. Pat. No. 2,504,497 discloses a new type of catalyst for dehydrogenation of alcohols to esters. The catalyst consists of a porous aluminum-copper alloy composition.
U.S. Pat. No. 3,188,330 discloses a liquid phase method for converting alcohols into ketones and esters in the presence of a carboxylic acid salt of a Group IIB metal, e.g., cadmium or zinc.
U.S. Pat. No. 3,452,067 proposes the use of a supported molybdenum sulfide catalyst for dehydrogenation of alcohols to esters in the vapor phase.
U.S. Pat. No. 3,639,449 discloses a process for converting alcohols to esters by reaction with molecular oxygen in the presence of a palladium or rhodium oxide catalyst.
As evidenced by the prior art disclosure, there is a continuing effort to develop improved catalysts and methods to ameliorate the disadvantages of known processes for converting alcohols into esters. A main disadvantage is the low selectivity conversion to the desired esters, and the concomitant formation of by-products such as acids, aldehydes, higher alcohols, and gaseous derivatives.
Accordingly, it is a main object of the present invention to provide a one-step vapor phase process for converting alcohols into carboxylic esters with a high conversion rate and a high selectivity.
It is another object of the present invention to provide a novel dehydrogenation catalyst which exhibits high selectivity for vapor phase conversion of primary alkanols into alkyl alkanoates.
Other objects and advantages of the present invention shall become apparent from the following description and examples.